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 [cpk] The Garage (v1.4, updated 17.10.16 - 73 cars) 
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Joined: Fri Jan 01, 2010 4:02 pm
Posts: 498
Post Re: [cpk] The Garage (v1.4, updated 17.10.16 - 73 cars)
Next time some Porsches and Bugattis.

Edit: I've just noticed that I mistyped Pagani specs, both in CE and in the table, it will be fixed with next update.
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The Garage 17.10.16.png
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Mon Oct 17, 2016 8:38 pm
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Joined: Fri Oct 10, 2014 9:55 am
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Post Re: [cpk] The Garage (v1.4, updated 17.10.16 - 73 cars)
More updates! :D The Elan and Europa are awesome, probably you was very inspired while making these Lotus. The same for the Pagani, while the Lykan has a very interesting construction. :scratch:
A small issue about the roof of the Superbird; often the head is visible but the problem can be simply solved by changing the positions of the roof's polys.


Tue Oct 25, 2016 1:51 pm
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Joined: Fri Jan 01, 2010 4:02 pm
Posts: 498
Post Re: [cpk] The Garage (v1.4, updated 17.10.16 - 73 cars)
Thanks for pointing this out, although roof's polys are ok, it's actually head position that's a bit too high. I'll correct that with the next update.

I didn't fell like making anything extraordinary while shaping Elan and Europa, their simple construction allowed to make these white stripes quite naturally. I struggled with finding polygons on Europa a bit, but all in all they were quite easy and straightforward - it's just the stripes what makes a difference. But Lykan was one of the most enjoyable ones to make, definitely.


Tue Oct 25, 2016 6:32 pm
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Joined: Thu Oct 20, 2016 11:28 am
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Post Re: [cpk] The Garage (v1.4, updated 17.10.16 - 73 cars)
This pack is awsome!!


Fri Dec 09, 2016 1:05 pm
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Post Re: [cpk] The Garage (v1.4, updated 17.10.16 - 73 cars)
I’ve seen some requests for explanation of my physics model (calculator) that was introduced with The Garage, so I finally decided to put it all together into a step-by-step instruction along with some insights.

1. Power and mass
It quickly became quite apparent to me that linear transformations (scaling by some constant) of car’s power and mass in real life is a very inflexible solution, which could yield satisfying results only for certain classes of vehicles. For example, formulas that would work nicely for, let’s say, race cars that have 500+ horsepower and <1000kg, would not function well for “normal” cars with much less power and weight of more than 1500kg - and conversely, linear formulas calibrated to road cars would make and sports car totally overpowered or even undriveable.
Therefore I use a formula that limits the leverage of high power and low mass and boost the performance of heavier, less powerful vehicles.

Power = 15*([Power in hp]+16)^(4/7)-75
Mass = 12*([Mass in kg])^(1/2)


These formulas are quite arbitrary indeed, and were obtained basically by trial and error until I came up with curves which I liked. After some testing I decided to stick to them and up to this moment I’m quite satisfied with the results.


2. Aero
Basically it is calculated as drag coefficient (cd) times frontal area, but both for many cars these parameters tend to be uncertain or even publicly unavailable. I use real drag coefficients whenever it is possible, and if it is not, I estimate it (sometimes simply by taking a random, but believable value), but in order to compensate the uncertainty, I use corrected frontal area calculated on the basis of 3D model which depends also on the car’s aerodynamic profile, precisely on the width of the car (W) and height of 3 points:

    A: height of the front of the car
    B: height of the bottom of the windshield (if it’s sufficiently far from the front, otherwise 0 (eg For trucks and buses))
    C: height of the roof

CFA = 1.5*W*(0.75A-B+1.25C)

The idea behind the formula is that the most important factor is the height of the car, but the aerodynamic drag also depends on how “quickly” the car “emerges” from the ground (low profile -> small A -> smaller resistance, for example for C Class cars). In the end, high B value indicates the low slope of the windshield which gives an aerodynamic advantage.
Then there is the final formula:

Air resistance = cd*CFA


3. Key assumptions regarding the steering
The model assumes that due to the technological progress, performance of cars in terms of grip and maneuverability increases over time – 1 year difference causes an increase of:
  • grip by 0.005
  • balance by 0.002
  • downforce by 0.5
In the following chapters the model year is denoted by MY.

The second underlying assumption is about the relationship between the wheelbase-to-length ratio (denoted as WtL) and car’s balance. The idea is that cars with high WtL ratio are more stable (slide less), but at the same time suffer from worse agility (less balance).

The third idea is the subdivision of vehicles into performance classes: So far I’ve been using the following classes:
    7+: prototypes
    6: GT cars
    5: Supersports cars
    4: Sports cars
    3: Sedans/saloons, muscle cars, hatchbacks
    2: City cars, family cars, SUVs
It is not set in stone though, and I frequently use fractions and assign cars to classes arbitrarily, to my liking. For example, Mazda 787B is 7, Ferrari LaFerrari is 5.5, Lexus LFA is 5.25, Aston Martin Vanquish is 4.25, Nissan 370Z is 3.5, Dodge Challenger R/T is 3, Land Rover Evoque is 2.5. Class should be assigned independently from the model year, so for example Ferrari 166MM is class 5 as well, even though it is not supercar by today’s standards – but this is compensated by the first assumption regarding the technological progress over time.

The fourth and last construct is the impact of car’s layout (engine position and drivetrain) on the steering. In a nutshell:
AWD cars have superior grip, balance and sliding
RWD cars have good grip and balance, but tend to slide more, while FWD cars have worse steering, but better stability.
RM is the “optimal” position and provides best balance between stability and steering. Engine too far to the front will disrupt the car’s steering ability.

As sketched above, layout will determine the “bonus” grip, balance and sliding of the car which will be added on top of the formula. The detailed parameters are presented in the tables below.
Attachment:
bonus.png
bonus.png [ 12.87 KiB | Viewed 228 times ]


4. Grip
Grip is calculated using the following formula:
Grip = 0.75 + 0.005*(MY-1950) + 1.5*(WtL-0.58) + 0.75 + 0.15*Class + Grip_bonus


5. Balance
Balance is calculated using the following formula:
Balance = 0.3 + 0.002*(MY-1950) + 0.66*(0.58-WtL) + 0.02*Class + Balance_bonus


6. Sliding
Sliding is calculated using the following formula:
Sliding = 0.05 + 0.5*(0.58-WtL) + Sliding_bonus


7. Downforce/wings
Downforce is calculated using the following formula:
Downforce = 0.5*(MY-1950)+1.5*(0.75+Class)^2 + Downforce_bonus

Where Downforce_bonus is a value allocated on the basis of car’s special qualities and features such as advanced bodywork or rear/fron wing (and their sizes). Usually it varies from 5 to 20, maybe 30 for prototypes.


That’s it – it may feel overly complicated, but in fact it uses the minimal amount of information (year, power, mass, layout, dimensions, drag coefficient) which are easily available, a bit of creator’s judgment and nothing more. Hope you'll find it useful.


Tue May 22, 2018 1:05 pm
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